1. Field of the Invention
The invention relates to packing and shipping cartons, and in particular concerns a plural-compartment carton formed from an integral flat piece of sheet material, and arranged with folds, glue joints and interlocking parts so as to erect into a reinforced and locked configuration. The canon has access openings in a front wall for compartments delineated by an internal partition. The partition has two panels doubled over a third panel attached between the front and rear walls. This three thickness partition is held by a slotted flap on one bottom panel or flap, that fits into a gap between the other bottom panels, thereby both locking the bottom in place and forming a central column that supports the carton, especially in the area weakened by the tear-out panels.
2. Prior Art
A two-compartment packing and shipping carton is advantageously used, for example, for packing complementary products. In the example of candy packaging, the two compartments can be used for comparable products with nuts and without nuts, respectively. Various other examples of alternative choice products are also possible. A known two-compartment container for shipping and display of alternative products comprises the combination of a separate cap-like top, which is relatively shallow, and a deep box-like bottom. At the packing line, the box-like bottom is filled with a product and the cap-like top is placed over the box-like: bottom for shipping or storage.
U.S. Pat. No.5,413,276--Sheffer discloses an improved two-compartment container that is formed from an integral piece of sheet stock, including the bottom, side walls and top, as opposed to a separate box and cap or cover. The sheet stock can be corrugated paperboard or the like. Such a carton can be creased, cut, perforated or similarly arranged to define relatively foldable panels that when erected become the six sides of the canon. In Sheffer '276, in addition to panels for the, six sides, covering panels are provided to seal over access openings in the front wall, and a further panel defines an internal web that subdivides the carton laterally into two compartments.
Cartons of this type are customarily handled several times between manufacture and retail use, being built in stages by the carton manufacturer and packer, respectively, and then partly disassembled by the retailer for access to the product. For example, the carton manufacturer cuts out the sheet material for the canon and makes a limited number of folds and attachments such that the carton can remain collapsed flat. Erection and the remaining attachments are left for when the canon is packed and sealed for shipment. The manufacturer cuts out a flat blank and forms certain folds generally forming the carton into a collapsed tube.
Abutting edges are affixed by glue, staple or tape joints or seams, while still permitting the carton to be collapsed flat for stacking a number of canons for shipping to the packer in a compact state. The carton can be made into a simple rectilinear tube or a bifurcated tube, folded flat between diagonally opposite corners in the manner of a parallelogram, leaving the top and bottom flaps unjoined to the front, back and sides. This allows a number of the cartons to be stacked flat to conserve space when shipping the cartons while empty.
The packer erects the collapsed carton into a rectilinear shape by pressing the diagonally opposite comers toward one another, and affixes the bottom panels by appropriate joints. The carton is then filled with product and the top panels are likewise attached to thereby seal the carton. Assembly of the bottom flaps and/or top flaps may include overlapping and affixing the flaps in various configurations. Bottom or top flaps that are attached to opposite side walls (e.g., the front and rear side walls) can be overlapped and attached, or flaps attached to adjacent side walls can be overlapped and attached such that the flaps are interleaved. Glue, staples, tape or other attachments can be employed. Not all the flaps need to be attached together. For example the front and rear opposite flaps can be attached, whereas the side wall flaps are simply rested internally against the attached flaps.
In order to achieve a one piece construction and a center divider panel, Sheffer '276 employs a wide bottom flap attached to the front side wall panel (i.e., the wall panel which has the tear-out perforations, and two half-width bottom flaps attached to the opposite wall panel (i.e., the rear wall panel). The rear wall panel is formed by two half-width segments that are glued or otherwise affixed to one another for closing the box into a collapsed tube. One of the rear wall segments is the proximal portion of a length of sheet material that continues from the proximal segment around a right angle fold into a distal panel extending from the attachment at the rear wall to the front wall of the carton. This distal panel is glued to the back side of the front wall and provides the central vertical web that subdivides the carton into two compartments. Each compartment has a front wall access opening extending up to the top edge of the front wall.
Accordingly, the '276 Sheffer carton provides, in a one-piece blank, a full width front wall panel with openings extending to the top edge of the front wall panel. The front wall panel is attached at vertical folds to two end wall panels, in turn attached at vertical folds to two half-width rear wall panels, one of which is further attached at a vertical fold to the compartment partitioning panel. Each of the wall panels, except for the partitioning panel, has an associated top flap and bottom flap in the flat blank, which flaps form the top and bottom closures. Not all the top and bottom panels are attached at folds to the immediately adjacent wall panel. In order to fold the top flaps into a U.sub.-- shaped configuration to cover the front wall access openings, some of the top panels are attached to adjacent flaps instead of to the adjacent wall panel, whereby the top flaps can cover the top and also fold down over the front and rear of the carton.
It is known to provide boxes with bottom panels that engage together to lock an erected box in a rectilinear configuration without the need for tape, glue, tabs or the like. For example, four flaps on a rectilinear container can be interleaved such that each flap rests over one flap adjacent to it on one side, and under the flap adjacent to it on the other side. The interleaved flaps thereby hold each other in place in a plane. In boxes having simple rectangular flaps, achieving this interleaved state is difficult using two hands because all four flaps must be positioned for interleaving while pressing them commonly inwardly. In U.S. Pat. No. 3,517,875--Wakefield, flaps protrude from the bottom of the front, rear and two side walls of a box and are arranged to lock in a complementary manner, with complementary shapes rather than rectangular shapes. When the flaps are folded inwardly downward in the proper order from inside the box, two opposite flaps partly overlap each other. The two remaining flaps are interleaved with the first two, and stop the lapped opposite flaps from passing the plane of the end. The four flaps are thus unfoldable to form a closed end or bottom that is interlocked to reside in the end plane without additional attachment means. However, the flaps can be pushed inwardly if the box is empty.
It would be advantageous to employ interlocking bottom flaps in a carton such as that of the Sheffer '276 patent, which can be assembled easily and locks the bottom flaps against any movement from the bottom plane. In addition, there is another problem to be addressed. Whereas two access openings or cutouts are provided in the front wall panel opening into the internal compartments, the front panel is relatively weak against collapse due to vertical forces. The strength of the carton against vertical forces (e.g., produced by stacking filled boxes in a display) is not fully corrected by the compartment subdividing panel because the front panel lacks a lateral connection between the end walls in the area of the cutouts, where the subdividing web is affixed. Thus the subdividing web can be bent or diverted toward either of the access openings without substantial resistance.
The access openings can be removed by the initial die cutting operation on the flat blank, or perforated and removable by a retailer after the packer fills the interior compartments with product. Whereas the top flaps associated with the front panel overlie the from panel, the access openings are preferably removed initially and closed by the overlying flaps. Nevertheless, when the overlying flaps and/or perforated access openings are laid open, the front central portion of the carton is relatively unsupported.
It would be advantageous if a collapsible carton blank could be formed in a manner that would better support the compartment subdividing web at the front, which would interlock readily at the bottom without requiring substantial effort, and which could be cut from a single integral flat sheet.